1,721,195 research outputs found
Comparative overview of the mechanisms of action of hormones and endocrine disruptor compounds
No full textEndocrine Disruptor Compounds (EDCs) are synthetic or natural molecules in the environment that promote adverse modifications of endogenous hormone regulation in humans and/or in wildlife animals. In the present paper, we review the potential mechanisms of EDCs and point out the similarities and differences between EDCs and hormones. There was only one mechanism, out of nine identified, in which EDCs acted like hormones (i.e., binding and stimulated hormone receptor activity). In the other eight identified mechanisms of action, EDCs exerted their effects either by affecting endogenous hormone concentration, or its availability, or by modifying hormone receptor turn over. This overview is intended to classify the various EDC mechanisms of action in order to better appreciate when in vitro tests would be valid to assess their risks towards humans and wildlife
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Characterization of bovine proteins potentially involved in reproduction : GPA2, GPB5, PDI, PEBP et Ubiquitin
No full textNous avons caractérisé cinq protéines bovines qui sont potentiellement impliquées dans la reproduction.Un travail de clonage a été initié qui permettra à terme de purifier les GPA2 et GPB5 recombinantes puis naturelles pour étudier leurs structures. GPA2 et GPB5 sont considérés comme les ancêtres moléculaires des sous-unités α et β des hormones glycoprotéiques. Nous avons montré la relative fragilité thermique de la structure quaternaire de la FSH bovine par rapport aux FSH ovine et humaine et nous avons étudié les propriétés enzymatiques de la PDI (Protein Disulfide Isomerase) en préalable à l’étude de l’activité PDI de GPA2/GPB5. Nous avons aussi purifié la phosphatidyl-ethanolamine-binding protein (PEBP) et l’ubiquitine testiculaires par chromatographie hydrophobe à très haute concentration de sulfate d’ammonium. A partir de la PEBP purifiée, on a produit des anticorps spécifiques chez le lapin qui nous ont permis d’être les premiers à développer un dosage ELISA fiable pour cette protéine.We characterized five bovine proteins that are potentially involved in reproduction. We started with the cloning of gpa2 and gpb5 cDNAs in order to eventually purify recombinant and natural GPA2 and GPB5 to study their possible quaternary structure. GPA2 and GPB5 are the evolutionary ancestors of Glycoprotein hormones α and β subunits respectively. Meanwhile, we have shown the relative quaternary structure fragility of bovine FSH compared to human and sheep FSH. We also studied the effect of endocrine disruptors on PDI (Protein Disulfide Isomerase) before addressing GPA2/GPB5 PDI activity of GPA2/GPB5 once purified.We succeeded to purify the phosphatidyl-ethanolamine-binding protein (PEBP) and ubiquitin from bovine testis by hydrophobic interaction chromatography at very high ammonium sulfate concentration and we produced specific antibodies (anti-PEBP) in rabbits that allowed us to be the first to develop a reliable Elisa assay for this protein
Neuroendocrine effects of endocrine disruptors in zebrafish (danio rerio) : study of GnRH system
No full textA ce jour, les effets des perturbateurs endocriniens (PE) sur les circuits neuroendocrines contrôlant la fonction de reproduction ont fait l’objet de très peu de travaux. Chez les vertébrés, l’élément majeur du contrôle central de la fonction de reproduction est la GnRH (Gonadotropin-Releasing Hormone). Le développement et l’activité des neurones à GnRH sont finement régulés, notamment par les hormones stéroïdes, ce qui les rend potentiellement sensibles aux PE. L’objectif de ce travail était d'étudier les effets neuroendocrines des xéno-œstrogènes chez le poisson zèbre (Danio rerio). Nous montrons que le 17α-éthinylestradiol (EE2) et le nonylphénol (NP) perturbent l'ontogenèse du système à GnRH au cours du développement précoce. De plus, nous démontrons que ces effets impliquent des récepteurs des œstrogènes. Parallèlement, nous mettons en évidence l’effet inducteur de l’EE2 et du NP sur l'expression de l’aromatase cérébrale, l’enzyme de synthèse des œstrogènes. L’ensemble de ces données souligne la nécessité de considérer les réseaux neuroendocrines comme des variables critiques et sensibles dans le domaine de la perturbation endocrinienne.Until now, studies dedicated to the actions of endocrine disrupting chemicals (EDCs) on the reproductive axis have focused on the gonads and peripheral organs leaving virtually unexplored their actions on neuroendocrine circuits controlling reproduction. In vertebrates, gonadotropin-releasing hormone (GnRH) is the key factor controlling the activity of the reproductive axis. The development and functioning of GnRH neurons are finely tuned, notably by sex steroids, making these neurons potential targets of EDCs. The aim of this work was to explore the neuroendocrine effects of xenoestrogens in the zebrafish (Danio rerio). We show that 17α-ethinylestradiol (EE2) and nonylphenol (NP) disrupts the ontogeny of GnRH system during zebrafish early life stage. Moreover, we demonstrate that these effects involve functional estrogens receptors. In parallel, we report the inducing effects of EE2 and NP on the expression of brain aromatase protein, the enzyme responsible for estrogen biosynthesis. Altogether, these results highlight the need to consider neuroendocrine networks as critical and sensitive endpoints in the field of endocrine disruption
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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